DESCRIPTION: (Adapted from the Applicant's Abstract.) The overall goal of the proposed research is a deeper understanding of the anatomical and neural bases of frequency selectivity in the vertebrate auditory system. In particular, the primary objectives of the proposed research are two: to provide insights into the mechanisms underlying stimulus interactions which affect tuning in the vertebrate auditory system, and to gain an understanding and appreciation of the cellular bases of frequency resolution. To accomplish the first of these objectives the investigators will (1) elucidate the underlying relationship between two-tone suppression and tuning in the auditory nerve by examining and comparing their temperature dependencies, (2) quantify the effect of contralateral sound on the tuning properties of single auditory nerve fibers, and (3) systematically study the effect of low-level vibratory stimulation on the auditory tuning properties of individual low-frequency auditory neurons. To carry out the second objective, the applicants will (1) precisely characterize membrane currents of auditory hair cells to determine their temperature dependencies, and thus to assess their contribution to tuning, and (2) relate anatomical fine structure (cell body dimensions, axon dimensions, innervation pattern) to tuning properties of identified auditory nerve fibers. Such data that result from this structure-function approach will be rich in implications regarding the anatomical and neural substrate underlying the processing of complex sounds, and that this work will serve as a model for understanding fundamental problems of human speech and music perception in adverse (noisy) environments.